Die casting apparatus



Se t. 16, 1969 c. F. FULGENZI ETAL DIE CASTING APPARATUS Filed Oct. 5.1966 FIGZ.

INVENTORYS CRESCENZO E FULGENZ/ JAMES a LAW PET R A. LERCH BY WFTORNE!United States Patent 3,467,171 DIE CASTING APPARATUS Crescenzo F.Fulgenzi, Parma, Ohio, James B. Law, New

Canaan, Conn, and Peter A. Lerch, Parma, Ohio, as-

signors to Union Carbide Corporation, a corporation of New York FiledOct. 3, 1966, Ser. No. 583,781 Int. Cl. B22d 17/04; F161: 15/18 US. Cl.164-316 4 Claims ABSTRACT OF THE DISCLOSURE A hot chamber die castingpiston type injection device having a resilient, refractory sealingmember positioned between the shot cylinder and gooseneck.

This invention relates to an improved apparatus for die casting highmelting point metals, such as aluminum and the like. More particularly,it concerns an improved means of forming a resilient, molten metalimpervious seal between the shot cylinder and the gooseneck of a diecasting apparatus adapted for use at high temperatures and pressures.

In the die casting art, it has long been desirable to cast high meltingpoint metals, such as aluninum and the like, by the so-calledhot-chamber technique, i.e., by a method which employs an apparatuswherein the shot cylinder is submerged in a pot of molten metal to becast.

Briefly, this apparatus comprises a pot of molten metal to be cast; asubstantially U-shaped, bifurcated gooseneck having a continuous openingtherethrough vertically suspended in the pot of molten metal, the innersurface of one furcation of the gooseneck being provided near its upperend with protrusion; a die cavity communicating with the upper end ofthe other furcation of the gooseneck; a shot cylinder provided with aflange which engages the protrusion in the gooseneck positioned in thegooseneck; and a pist on communicating with the shot cylinder which whenadvanced into the shot cylinder causes the molten metal therein to bemoved into the die cavity to produce the desired casting.

It is essential to the successful operation of the beforedescribed diecasting apparatus that a positive seal be achieved and maintainedbetween the protrusion in the gooseneck and the flange of the shotcylinder. If this seal is not maintained, it is almost impossible toproduce a casting having the desired characteristics.

Heretofore, this seal had been achieved by providing the mating parts ofthe shot cylinder and gooseneck with lapped surfaces which were forcedtogether by means of a mechanically applied pressure. However, this typeof seal does not always perform satisfactorily, especially when thegooseneck and shot cylinder are made from dissimilar materials.

For example, it is common practice when die casting high melting pointmetals such as aluminum and the like to fabricate the shot cylinder froma ceramic material such as titanium diboride and the gooseneck fromferrous material such as cast iron. Attempts to pressure seal lappedsurfaces of this type have met with little success due to the fact thatthe individual materials of construction possess different thermalexpansion characteristics which cause the so-formed joint to separate atits interface when it is exposed to fluctuating temperatures.

Accordingly, it is the principal object of the invention to provide animproved die casting apparatus in which a resilient, molten metalimpervious seal is readily maintained between the shot cylinder and thegooseneck at elevated temperatures.

ice.

Other objects of the invention will become apparent from a reading ofthe specification and claims taken in conjunction with the drawingswherein:

FIGURE 1 is a side elevational view partly in section of a die castingapparatus embodying the invention.

FIGURE 2 is a somewhat enlarged cross-sectional view showing thepositioning of a resilient, molten metal impervious sealing memberbetween the shot cylinder and the gooseneck of a die casting apparatusembodying the invention. FIGURE 3 is a cross-sectional view whichillustrates a slightly modified means of positioning the sealing memberbetween the shot cylinder and the gooseneck of a die casting apparatusembodying the invention.

Briefly, the objects of the invention are accomplished by a conventionaldie casting apparatus wherein a resilient, molten metal impervioussealing member is positioned between the shot cylinder and the gooseneckin such a manner as to permit the shot cylinder and the gooseneck tothermally expand or contract without disrupting the seal formedtherebetween.

With reference to the drawings, as shown in FIGURE 1, a conventional diecasting apparatus, in general, consists of a holding furnace 10 whichsupports a melting basin or port 12 containing the molten metal to becast 13. A bifurcated gooseneck 14 is suspended within the pot 12 andcommunicates at one of its ends with a die cavity 16. The die cavity isconventional in design and will not be shown in detail. The inner wallof the opposite end of the gooseneck 14 is provided with acircumferential protrusion 18 which is adapted to receive and hold aresilient sealing member 17. The shot cylinder 20 is provided with anoutwardly extending flange 21 which engages the sealing member 17. Apump assembly is positioned inside the upper end of the gooseneck 14 andon top the shot cylinder 20. The pump assembly is so positioned as tocause the sealing member 17 to be somewhat compressed between theprotrusion 18 in the gooseneck 14 and the flange 21 of the shot cylinder20 to form a resilient, molten metal impervious seal between the shotcylinder and the gooseneck. The pump assembly comprises a housing 22which is disposed inside of the upper portion of the gooseneck 14 incontact with the flanged shot cylinder 20 and a piston 24 whichcommunicates with the bore 23 of the shot cylinder 20. The means foractuating the shot cylinder are well known in the art and will not bedescribed.

Referring to FIGURE 2, there is shown in detail one of several meansprovided by the invention for forming a resilient seal between the shotcylinder 20 and the gooseneck 14. The gooseneck 14 is provided with acircumferential protrusion 18 which is adapted to receive and hold theresilient ring shaped sealing member 17. The flange 21 of the shotcylinder 20 rests upon the sealing member 17. A seal is facilitatedbetween the gooseneck and the shot cylinder by means of a housing 22which exerts a downward pressure upon the flanged shot cylinder. Theresilient sealing member 17 is preferably composed of a flexible form ofexpanded graphite which will be described in detail later. A piston 24is shown communieating with the bore 23 of the shot cylinder 20 whichwhen advanced in the shot cylinder causes molten metal to be moved intoa die cavity (not shown) to produce the desired casting.

FIGURE 3 concerns a modified means of positioning the shot cylinder 20within the gooseneck 14. The gooseneck 14 is provided with an inclinedprotrusion 16. A correspondingly shaped resilient gasket 26 engages thisprotrusion and the flange 21 of shot cylinder 20 rests upon the gasket26 thereby forming a seal between the shot cylinder and the gooseneck.

In the actual operation of a die casting apparatus embodying theinvention, the shot cylinder and gooseneck are positioned below theliquid level of the molten metal bath and gravity filled by withdrawingthe piston from the shot cylinder. Once the shot cylinder and gooseneckare filled, the piston is then forced into the shot cylinder to commencethe movement of the molten metal therein toward the die cavity. As thepiston continues its downward movement into the shot cylinder, anincreasing fluid pressure is exerted on the joint area between thegooseneck and the shot cylinder. However, as this area is positivelysealed by means of a molten metal impervious sealing member, the metalto be cast is accordingly directed into the die cavity under a uniformpressure to insure that a casting having the desired physicalcharacteristics is obtained.

An apparatus as described in FIGURE 1 equipped with a ring shapedsealing member composed of expanded graphite positioned between atitanium diboride shot cylinder and a cast iron gooseneck was employedto produce ing member of expanded graphite. One and one-half poundaluminum castings were produced by this apparatus at the rate of 300 perhour. A total of 41,650 castings were produced during this run.Essentially all castings were of excellent quality.

The term expanded graphite as used herein and in the appended claims ismeant to include any form of graphite which has been treated with areagent which causes it to expand and have a thickness or c dimensionwhich is at least twice and preferably eighty times that of its originalthickness.

A method for producing such a form of expanded graphite is disclosed inUS. Patent 1,137,373 which issued to J. W. Aylsworth on April 27, 1915.

Briefly, the method disclosed in the Aylsworth patent comprises thesteps of subjecting graphite particles to the action of a strongoxidizing agent such as a mixture of sulfuric and nitric acids, heatingthe so-treated soggy mass at a temperature below the boiling point ofthe acid mixture, washing the treated graphite to remove any excessacids or salts therefrom and then further heating the washed graphite tored heat until there has been suflicient expansion of the graphitematerial. The resultant expanded graphite material is then mixed with abinder and formed into the desired configuration by conventional moldingtechniques.

Another method of producing expanded graphite is disclosed in co-pendingUS. patent application Ser. No. 273,245, entitled Chemical Products andProcesses. This application is assigned to the same assignee as thepresent invention. The form of expanded graphite disclosed in thisapplication is unique in that it is self-binding, i.e., it can be formedinto the desired shape without the use of an additional binder.

Briefly, the process taught in co-pending application Ser. No. 273,245comprises treating graphite particles with an oxidizing agent such as amixture of sulfuric and nitric acids, washing the oxidized soggygraphite particles to remove any excess acids or salts and rapidlyheating the so-treated graphite particles to a temperature of about 1000C. to effect a substantially instantaneous expansion of the graphiteparticles. The resultant expanded graphite particles are then formedinto the desired shape by conventional molding techniques.

Expanded graphite produced by the latter technique is preferred as thematerial of construction for the sealing member employed in theapparatus of the invention as this form of expanded graphite isinherently adhesive and attaches itself to the mating surfaces beingsealed and thereby further resists leakage which might occur due tocapillary action.

It will be appreciated by those skilled in the art that the componentparts of a conventional die casting apparatus can be fabricated from amyriad of different refractory materials. All that is required is thatthe selected material of construction be resistant to the action of themetal being cast. When die casting aluminum, it has been found to behighly desirable to employ a titanium diboride shot cylinder and a castiron gooseneck although other like materials have been used with equalsuccess.

What is claimed is:

1. In an apparatus for casting a molten metal into a die cavitycomprising:

(a) a pot containing molten metal;

(b) a bifurcated, substantially U-shaped gooseneck having an openingextending therethrough vertically positioned in said pot, said gooseneckbeing provided with a protrusion extending from its inner surface inclose proximity to one of its ends, the opposite end of said gooseneckcommunicating with said die cavity;

(c) a shot cylinder having an outwardly extending flange engaging saidprotrusion in said gooseneck and depending into said gooseneck; and

(d) a piston communicating with said shot cylinder which when advancedinto said shot cylinder causes the molten metal in said shot cylinder tobe moved into said die cavity to produce a casting;

the improvement which comprises:

(e) a resilient, refractory sealing member positioned upon the upperportion of said protrusion in said gooseneck, said sealing membercontacting and supporting said shot cylinder thereby forming a sealbetween said gooseneck and said shot cylinder which is impervious to themolten metal being cast and uneffected by the stresses induced in saidsealing member due to the thermal characteristics of said shot cylinderand said gooseneck.

2. The apparatus of claim 1 wherein said sealing member is composed ofexpanded graphite.

3. The apparatus of claim 1 wherein:

(a) said gooseneck is provided on its inner surface with an inclinedprotrusion which slopes away from the upper opening in said gooseneckand,

(b) said seal member is correspondingly shaped to engage said inclinedprotrusion and support said shot cylinder.

4. The apparatus of claim 1 wherein:

(a) said gooseneck is composed of iron;

(b) said shot cylinder is composed of titanium diboride; and (c) saidsealing member is composed of expanded graphite.

References Cited UNITED STATES PATENTS 1,137,373 4/1915 Aylsworth 264-42X 2,145,553 1/1939 Morin 103-153 2,390,263 12/1945 Mills 164-3162,835,005 5/ 1958 Green 222-385 3,209,418 10/1965 Smith 164-3183,315,651 4/1967 Dangauthier 92-171 X 3,319,702 5/1967 Hartwig et al.164-316 J. SPENCER OVERHOLSER, Primary Examiner R. S. ANNEAR, AssistantExaminer US. Cl. X.R. 92-165, 169, 171

